Here are some of my favorites (some probably are repeated):
Beethoven -
Fur Elise

Sonata Op. 13, 2nd Movement
Sonata Op. 28, 4th Movement
Sonata Op. 53, 3rd Movement
Sonata Op. 90, 2nd Movement
Sonata Op. 109, 3rd Movement
Sonata Op. 110, 3rd Movement
Piano Concerto #5, 2nd Movement
9th Symphony, Ode to Joy
Mendelssohn -
Rondo Capriccioso (Andante)
Liszt -
Liebestraum in Ab
Sonata, many of the slow themes
Chopin -
Polonaise (Heroic)
Nocturne in E Flat
G Minor Ballade
Schumann -
Traumerei
Grieg -
Piano Concerto, 3rd Movement slow theme
Tchaicowsky -
Romeo and Juliet
Piano Concerto 1, Introduction
Capriccio Italian
Dvorak -
New World Symphony, 2nd Movement
Saint-Saens -
Organ Symphony, 2nd Movement, 4th Movement (main theme of the symphony)
Satie -
Gymnopedie No. 1
Gershwin -
Rhapsody in Blue, slow theme
Debussy -
Reverie
Suite Bergamasque, Clair de Lune
Rachmaninoff -
2nd Piano Concerto, 3rd Movement
3rd Piano Concerto, 1st Movement slow theme, and the very end
Rhapsody on a Theme by Paganini, 18th Variation
Godowsky -
Polonaise
Poem #2 - Avowel
Ein Daemmerungsbild
Busoni -
Concerto, all of the themes throughout the concerto that are combined in the last movement
This list doesn't even scratch the surface.